Existing battery management algorithms rely upon empirical correlations between the cell voltage and the load profile. This approach limits the predictive ability of the battery management system to forecast remaining useful life of a battery in a vehicle, or the range available at any given instant when the vehicle is in operation.

Description

Scientists at the National Renewable Energy Laboratory (NREL) have developed software that incorporates material parameters, electrochemical characteristics and thermal design aspects used to build the cells, and thus provides a customized and physics-based estimate of remaining capacity or useful life – thus enabling the use of an extended window of operation for the battery, obliterating the need for over-designing the battery (to compensate for its limited ability to forecast performance dynamically) and thus minimizing the weight and cost of battery packs.

Benefits

This software is specifically light-weighted for hardware-in-the-loop simulations and implements the thermal and electrochemical laws of conservation in a format that can be readily implemented onto hardware for interfacing with and controlling lithium ion cells. The model can:

Provide real-time updates of electrochemical states when interfaced with a battery

Accept a set value for current (or voltage), the initial states within the positive and negative electrodes, and the initial cell and ambient temperatures as input, and predict the voltage (or current) under these conditions after a specified duration

Determine whether or not a lithium ion cell can deliver the power requirement for a given set of initial conditions for the cell

Output the distribution in temperature, current and potential across the electrodes for a given load profile

The software has been used to demonstrate 50% reduction to charge times of lithium ion cells and about 10% reduction to the size of a PHEV battery pack.